This invention concerns a rectifier for regulating or stabilizing the flow of a liquid or gaseous fluid circulating in a tubular duct or pipe, where the fluid flow is irregular or turbulent as a result of passing through an obstacle such as a bend, a junction in the duct, or a valve. The use of such a rectifier to facilitate the measurement of fluid flow constitutes a particularly important application since, as is well known, measurements conducted using a flow meter provide a more correct indication if the flow is completely configured as a very flat profile with a flow direction parallel to the pipe axis.
A variety of rectifiers of this type are already on the market, e.g., perforated disks, screens, metal fabrics, or a combination of these components, the entire assembly being inserted into the duct. For example, a known rectifier is composed of a screen to the upstream surface of which is attached a perforated disk whose holes have a diameter which increases toward the center and diminishes toward the circumference.
However, all of these rectifiers have several major disadvantages:
Their effectiveness is relatively low, since it has been found that the fluid flow remains irregular over a length of the duct downstream from the rectifiers and measuring more than 10 D, where D is the interior diameter of the duct. Accordingly, a flow meter can be installed only at one end of a pipe length greater than 10 D, thereby creating bulky fittings.
The flow-rate pattern obtained downstream from these rectifiers has a rounded profile, signifying that there are sizable differences between the rate of flow along the axis of the duct and the rate of flow in proximity to the wall.
The manufacturing cost is high, especially as regards the rectifier according to the last of the embodiments above, because of the uneven distribution of hole diameters over the disk surface.
All such rectifiers must increase in thickness as the duct diameter becomes greater, this thickness varying between approximately 0.13 D and 2 D. It is obvious that, in the case of large-diameter pipes and thus of very thick rectifiers, the latter must be permanently installed in the pipe since it is virtually impossible to take them out.